Method of making turbine blades



Feb. 25, 1930. RAY 1,748,364

METHOD OF MAKING TURBINE BLADES Filed Oct. 9, 1928 Fig.4. Fig.5; Fi..6.-

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wnmzssss; INVENTOR I 5 a V5 72 ATTORNEY Patented Feb, 25, 1930 j UNITEDSTATES PATENT OFFICE JAMES L. BAY, OF SWARTHMORE, PENNSYLVANIA, ASSIGNORTO WESTINGHOUSE ELECTRIC &-MANUFACTUBING COMPANY, A CORPORATION OFPENNSYLVANIA METHOD OF MAKING TURBINE BLADES Application filed October9, 1928. Serial No. 311,323.

My invention relates to elastic fluid turbines and more particularl tothe blading thereof, and it has for an object, to improve the efiiciencyof apparatus of this character. In turbine blades of a tapered, hollowconstruction, the metal is more efficiently disposed with respect to theneutral axes and the requisite-strength may thus be obtained withminimum weight. Inasmuch'as the centrifugal forces, and thestressesresulting therefrom, are directly proportional to, and varydirectly as the weight, it becomes important, particularly with thelarger blades, such as the low pressure reaction blades, to reduce theweight as much as possible in order to keep the centrifugal stresseswithin permis sible limits. By decreasing the weight of the blades, itis possible to use a rotor of relatively light construction and thus, togenerally reduce the weight, as well as the cost, of

' a turbine and hence, to improve the construction of apparatusof thischaracter. Vhile these advantages may be gained by using hollow blades,of variable cross-section, proportioned to have the proper strength'ateach transverse section, the manufacture of such blades has, therefore,been quite expensive and tedious work. Y

It is a more particular object of this invention therefore, to provide asimple and inexpensive method by whichturbine blades of the tapered,hollow type of construction may be made with a high degree of accuracy.

This and other objects are effected by my lowing description and claimstaken in connection with the accompanying drawings,

forming a part of this application, in which: Fig. 1 is an elevation ofa blade blank;

Fig. 2 is an end view of Fig. 1;

Fig. 3 is a View of the blank shown in Fig.

blade; and, I Figs. 9, 10, 11 and 12are sections on invention as will beapparent from-the folthe lines IXIX, X'X, XIXI and XIIXII, respectively,of Fig. 8.

In accordance with my improved method, the blade-forming portion of ablade blank, which may be cylindrical, is hollowed out by some simplemethod, as by boring, and the root-forming portionand the base of theblade are forged to substantially their finished form; while theremainder, or outermost portion of the blade is flattened out to a shapewhich approximates its finished form but which is somewhat smaller. Theblade blank is then placed in a finishing die and the hollow portion isexpanded by fluid pressure until the blade properly fills the die. Inthis way, ablade may be made of a tapered, hollow construction which isproperly proportioned at its various transverse sections to have therequisite strength and, at the same time, this procedure is relativelyinexpensive and easy to carry out, as,no diflicult machining, or forgingoperations are required.

In the drawing, the blade blank is indicated generally at 10, in Fig. 1,and this blank may conveniently be cylindrical, as shown. and mayconsist of a blade-forming portion 11, and a root-forming portion 12 anda suitable extension, or tong hold 13 may project from the root-formingportion 12. In preparing this blank, the blade-forming portion 11 ishollowed out in any approved manner, as by boring as indicated at 14, toprovide a hollow blade section. The taper is secured either by turningthe outside of the blade-, forming portion to the proper'taper, or bytaper boring of this" portion, or by'both of these operations, as shown.

The blade is next forged to the form shown in-Fig. 3, wherein it will benoted (Figs. 4 and 5) that the root-forming portion as well asthe baseof the blade is forged to the finished form, while as will be apparentfrom Figs. 6 and 7, the-thin cylindrical outer portion is closed downand bent to a shape which 95 approximates the shape of the finishedblade but which is of smaller cross section than the 60 low cylindricalblade section, tapering blade. The blade is then placed in a finishingdie and the partially formed portion is expanded to fillthe die by fluidpressure acting through the passage 17. In this way, the

blade is accurately formed to the proper proportions and of variablecross section, as

shown in Figs. 8 to 12. It will be apparent that by using fluid pressureto expand the unfinished portions of the blade, practically any amountof pressure may be provided and thus, it is possible to expand the bladeWhile cold'and also to properly regulate the expanding force so that themetal may be gradually expanded and thus, to avoid rupture of theexpanded portion and 'to' assure that the blade willtake the shape ofthe die.

While I prefer to make this blade by apply--' ing fluid pressurethrough' e root portion to the interior of the blade, 't will be obviousthat the passage 17 as well as the weld 16 may be omitted, if desired,and that fluid pressure may then be applied from the open end, or tipof-the blade. While I have. shown my invention in but one form, it willbe obvious to those skilled. in the artthat it is not so limited, but issusceptible of various changes and modifications wvithout departing fromthe spirit thereof, and- I desire, therefore, that only. suchlimitations shall be placed thereupon as are imposed by the prior artoras are specifically set forth in the appended claims. What I claim is:

1. The-method, of making a turbine blade which comprises boring theblade-forming portion of a blade blank from the tip toward the basethereof to provide a hollow ?blade section, forging the root tosubstantially its finished form and closing downthe hollow blade sectionto a shape which approximates '50 the shape of the finished blade butwhichiis' of smaller'c'ross section than the finished blade, holding theblank in'a die and using fluid pressu-reto ex and the blade section tocause the latter to 11 the die.

2. The method of; makin a turbine blade which comprises forming t eblade portion of a blade blank into a substantially cylindrical shape,boring the blade portion from the tip toward the base thereof to providea 1:311-

e blade section, forgin the root of the blade to substantially finisher?form and closing down the cylindrical blade section to a shape whichapproximates the'shape of the finished blade 35 but which is of smallercross section than the finished blade, holdin the blank in a finishingdie and applying uid pressure to the interior of the blade sectionto.expand the latter' until it properly fills the die.

3. The method of making a turbine blade which comprises boring the bladeportion of a blade blank from the tip toward the base thereof to providea hollow blade section, forging the root and the base of the blade tosubstantially finished form, closing down and bending the remainder ofthe hollow blade section to a s'hapewhich approximates the shape of thefinished blade but which is of smaller cross section than the finishedblade, working down the\inlet and outlet edge portions until they arerelatively thin, holding the blank in a finishing die and applying fluidpressure to the interior of the blade section to expand the latter untilit-properly n fills the die.

4. The method of making a turbine blade which comprises boring the bladeportion of v a blade blank from the tip toward the base thereof toprovide a hollow blade section, tapering the outside of the hollow bladesection, forging the root and the base of the blade section tosubstantially finished form, closing down andbending the remainder ofthe blade section to a shape whichapproximates the shape of the H ishedblade but which is of smaller cross se tion than the finished blade,holding the blade in a finishing die and apblade section until thelatter is sufiiciently expanded to properly fill the die.

5. The method of making a turbine blade which comprises boring the bladeportion of ablade blank from the ti toward the base thereof to provide ahol ow blade section,

tapering the inside of the hollow; blade section, forging the root andthe base of the blade section to substantiall finished form, closingdown and bending t is remainder of the blade section to a shape whichapproxi- 'niates the shape of the finished blade but which is.0f smallercross section than the finished blade, holdin the blade in a finishingdie and applying flui pressure to the interior of the blade sectionuntil the latter is sufiicientlv expanded to properly fill the die.

6. The method of making a turbine blade which comprises boring the bladeportion of a blade blank from the tip toward thebase plying fluidpressure to the interior of the e thereof to provide a hollow bladesection, ta-

peringthe outside and inside of the hollow blade section, forging theroot and the base of the blade section to a shape which approximates theshape of the finished blade but which is ofsmaller cross section thanthe finished blade, holdin the blade in a finishing die and applyingfluid pressure to the interior of the blade section until the latter issufii clently expanded to properly fill'the die.

7. The method of making a turbine blade which comprises boring the bladeportion of 4 a blade blank from the tip toward the base thereoftoprovide a hollow blade section,

tapering the hollow blade section from the base toward the tip thereof,forging the root and the base of the blade'to substantially finishedforin, closing down and bending the remainder of thehollow blade-sectionto a shape, which, approximates the shape of the finished blade butwhich is of smaller cross sect-ion than the finished blade, working downthe inlet and outlet edge portions until they are relatively thin,holding the blank in a finishing die and applying fluid pressure to'which comprises boringthe blade portion of a blade blank from the tiptowardthe base i the sha the interior of the blade section to expand thelatter until it properly'fills the die.

v 8. The method of making a turbine blade thereof to provide ahollow'blade section, forging the root to substantially finished form,closing down and bending the hollow blade sectionto a shape which aiproximates of the finished blade ut which is of sma ler cross sectionthan the finished blade, sealing shut the hollow interior of the bladeat the tip thereof, forming a pa:-

sage through the root to the interior of the hollowblade section,holding the blade in a finishing die and applying fiuid pressure throughsaid passage to the interior of the hollow blade secti n until thelatter properly fills thedie. 5

9. The method of making a turbine blade whioh comprises boring the bladeportion of a blade blankfrom the tip toward thebase thereof to provide ahollow blade section, tapering the hollow blade section from the ,basetoward the tip, forging the root'and the scribed 192s.

base of the blade substantially finished form, closing down and bendingthe remainder of the hollow blade section to a shape whichappro'xiinates the shape of the finished blade but which is of .sma

r cross section than the finished blade, sealing shut the hollowinterior of the blade at the tip thereof, forming a passage through theroot to the hollow interior of the blade section, holding-the blade in adie'and applying fluid pressure through said passage to the interior ofthe hollow blade section until the latter is sufficiently expanded toproperly fillthe'die. v

. In testimony whereof, I have hereunto submy name this 2nd day ofOctober,

JAMES L. RAY.

